Improving public understanding of probability and risk with special emphasis on its application to the law. Why Bayes theorem and Bayesian networks are needed

Saturday, 14 June 2014

Daniel Kahneman at the Hebrew University Jerusalem

I have just returned from the workshop on "Behavioral Legal Studies - Cognition, Motivation, and Moral Judgment" at the Hebrew University in Jerusalem, Israel. I was especially interested in seeing Daniel Kahneman open the workshop with "Reflections on Psychology, Economics, and Law". Kahneman won the 2002 nobel prize in economics and was also recipient of the Presidential Medal of Freedom from President Obama in 2013.

Kahneman is, of course, very well known for his pioneering work with Amos Tversky and Paul Slovic (who also spoke at the workshop) on cognitive bias (which has greatly influenced our own work on probabilistic reasoning in the law) and also prospect theory (for which he won the Nobel prize). Kahneman's 2011 book "Thinking, Fast and Slow" which summarises much of his work, has sold over one and a half million copies. The book is based on the idea that, when it comes to assessment and decision-making, people are either system 1 (fast) thinkers or system 2 (slow) thinkers. The former act on instinct and often get things wrong while the latter are more likely to get things right because they think through all aspects of a problem carefully. While I think Kahneman's book is a very good read, I personally do not find the fast/slow classification of decision-makers to be especially helpful. Nevertheless, a lot of the speakers at the workshop used it to inform their own work.

Kahneman's presentation was in the form of an interview by Prof. Eyal Zamir and Prof. Ilana Ritov (both of the Law Faculty at the Hebrew University) asking the questions. Kahneman nicely summarised the main results and achievements of his career and was humble enough both to give credit to his co-researchers and also to admit that some of his theories (such as on gambling choices) had subsequently been proven to be false.

Audience at Kahneman interview

Kahneman touched on one of the key points in his book that I find problematic, namely his rejection of what he calls 'complex algorithms'; his argument is that any assessment/decision problem that involves expert judgment should not involve many variables because you can always get just as good a result with a simple model inolving no more than three variables. While I agree that any problem solution should be kept as simple as possible, a crude limit to the number of variables directly contradicts our Bayesian network approach, where models often necessarily involve multiple variables and relationships derived from both data and expert judgment. The important point is that the 'complex algorithms' we use are just Bayesian inference - of course if you had to do this 'by hand' then it would be disastrous, but the fact that there are widely available tools means the algorithmic complexity is completely hidden. Crucially, we have shown many times (see for example this work on evaluating forensic evidence) that the Bayesian network solution provides greater accuracy and insights than the commonly used simplistic 'solutions'.

Much of the theme of what Kahneman spoke about (and which was also a key theme of the workshop generally) was about 'moral judgment' - he cited the radically different legal responses to murder and attempted murder as an example of irrational (and possibly immoral) decision-making. The problem with 'moral judgment' - and the continually repeated notion of 'what is good for society' is that most academics have a particular view about these that they assume are both 'correct' and universally held. Hence, much of what I heard during the workshop was politicized and biased. This was also evident in Kahneman's answers to audience questions following the interview. I actually asked Kahneman what his rationale was for concluding that President Obama was a system 2 thinker. Bearing in mind that system 2 thinkers are supposed to be 'good' decision makers compared with system 1 thinkers, his response was clearly popular with many in the audience, but actually surprised me because it seemed to be purely political; he basically said something like "you only have to compare him with the previous guy (Bush) to know the difference".

Kahneman also gave his views on how conflicts (like that of Israel and its enemies) could be solved, which I found were naive and possibly contradictory to his own work in psychology. His theory is that both 'sides' in a conflict are rational, but believe they are responding to the actions of the other side - so all you need to do is to make both sides aware of this.

There was a very nice reception for invited workshop participants after Kahneman's interview, but Kahneman himself had to rush off to another meeting and he took no further part in the workshop.

1 comment:

Amazing Stuff. This book is "unputdownable". It seems author as an individual was always curious to know the working of human brain and his curiosity led him to a discover the information which he has shared in a nicely written format. Each chapter of the book will take you closer to your very own grey matter and the kind of flash decisions we all make albeit on the wrong side in-spite of having the requisite knowledge and right IQ. Many of us make mistakes without realizing it and this book brings out this aspect very very nicely .

Martin Neil

About Me

Norman's experience in risk assessment covers application domains such as legal reasoning (he has been an expert witness in major criminal and civil cases), software project risk, medical decision-making, vehicle reliability, football prediction, transport systems, and financial services. Norman has published over 130 articles and 5 books on these subjects